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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of ambient ozone using a nitrite-coated filter (1993)
    s.l. : American Chemical Society
    Analytical chemistry 65 (1993), S. 209-214 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00051a004
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  • 2
    Electronic Resource
    Electronic Resource
    Renin Inhibitor: Relationship Between Molecular Structure and Oral Absorption (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1443-1447 
    Details
    ISSN: 1573-904X
    Keywords: renin inhibitor ; cyclodextrin ; intestinal permeability ; in situ intestinal loop ; oral absorption ; first pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Common problems in developing renin inhibitors are low solubility, insufficient oral absorption, and fast hepatic clearance. We focused on the molecular structure of renin inhibitors to overcome these problems. Cyclodextrins (CD) improved the low solubility of renin inhibitors, with β-CD showing the best ability to dissolve renin inhibitors. The intestinal absorption of renin inhibitors varied with both their solubility and molecular structure. Coadministration of β-CD improved the intestinal absorption of some renin inhibitors with low solubility as measured by transport into the mesenteric vein in the absorption experiment using the rat intestinal loop. Substitutions at both the N and C terminals was essential for absorption from the small intestine. A naphthyl group at the N-terminal further improved intestinal absorption. A carrier system appeared to be involved in the intestinal absorption of some renin inhibitors. N-methylation at the amide bond of thiazolylalanine suppressed the high hepatic clearance of one of the test compounds 18 which was well absorbed from the small intestine and it improved its oral bioavailability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018948007419
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  • 3
    Electronic Resource
    Electronic Resource
    Renin Inhibitor: Transport Mechanism in Rat Small Intestinal Brush-Border Membrane Vesicles (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1448-1451 
    Details
    ISSN: 1573-904X
    Keywords: renin inhibitor ; rat intestinal brush-border membrane vesicle ; BBMV ; proton coupled uphill transport ; peptide carrier system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport characteristics of the renin inhibitor ((3S,4S)-4-[N-morpholinoacetyl-(l-naphthyl)-L-alanyl-N-methyl-(4-thiazolyl)-L-alanyl]amino-3-hydroxy-5-cyclohexyl-l-(4-pyridyl)-l-pentanone; CH3-18) in rat small intestinal brush-border membrane vesicles (BBMV) were examined by a rapid filtration technique. The uptake of CH3-18 was markedly stimulated by an inwardly directed H+ gradient (pH 7.5 inside, pH 5.5 outside) and showed an uphill transport. It was competitively inhibited by tripeptides and tetrapeptides, but not by amino acids or dipeptides. A countertransport effect on the uptake of CH3-18 was observed in the vesicle preloaded with a tripeptide. Effects of the fragments of several renin inhibitors were evaluated by their inhibitory and countertransport effects on the uptake of CH3-18. The morpholino group at the N-terminal was found to be important for the uptake of CH3-18.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018900124257
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristics of Ceftibuten Uptake into Caco-2 Cells (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1761-1765 
    Details
    ISSN: 1573-904X
    Keywords: ceftibuten ; Caco-2 ; uptake ; brush-border membrane vesicles ; oligopeptide ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characteristics of ceftibuten uptake into Caco-2 cells grown in a collagen-coated dish were examined. Ceftibuten showed stereoselective and pH-dependent uptake. The pH-dependency of ceftibuten was more marked than that of cefaclor or cephalexin, but all three antibiotics showed maximal uptake at pH 5.5. Ceftibuten uptake was linear for the initial 1 hr and then reached a plateau. The initial uptake (15 min) was markedly reduced by the addition of 2,4-dinitrophenol or FCCP (a protonophore), or by lowering the incubation temperature. The uptake of ceftibuten into the brush-border membrane vesicles prepared from cultured Caco-2 cells showed an overshoot in the presence of an H+-gradient. These findings indicated that the uptake of ceftibuten was energy-dependent, especially H+-gradient-dependent. Uptake inhibition by various compounds was compared using Caco-2 cells. Amino acids and a tetrapeptide did not inhibit uptake, whereas di- or tri-peptides were effective inhibitors. These observations suggest that ceftibuten is taken up by a carrier-mediated transport system(s) for dipeptides. Various antibiotics differed in their ability to inhibit uptake, with cyclacillin showing maximum inhibition. Differences in the inhibitory effect may be accounted for by the heterogeneity (multiplicity) of the transport systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018919517839
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  • 5
    Electronic Resource
    Electronic Resource
    Transport Characteristics of S-1090, A New Oral Cephem, in Rat Intestinal Brush-Border Membrane Vesicles (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1488-1492 
    Details
    ISSN: 1573-904X
    Keywords: S-1090 ; transport ; brush-border membrane ; oligopeptide ; histidine ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Elucidating the transport characteristics of S-1090, a new orally active cephalosporin in rat small intestinal brush-border membranes. Methods. A rapid filtration technique. Results. The uptake of S-1090 was stimulated by an inwardly directed H+-gradient, but did not show overshooting uptake. To investigate the transport system, the inhibitory and countertransport effects of various compounds on S-1090 uptake were examined. Although the dipeptides and tripeptides composed of amino acids with aliphatic side chains did not inhibit the uptake of S-1090, those having histidine, proline or tryptophan as the N-terminal amino acid showed an inhibitory effect. Among the oral cephems tested, ceftibuten showed marked inhibition, while cefaclor and cephalexin had no inhibitory effect. Countertransport effects on S-1090 uptake were observed only when the vesicles were preloaded with histidyl peptides such as His-Gly or His-Ala, while other compounds which exhibited inhibition had no countertransport effect. Conclusions. Based on the above results, there seems to be heterogeneity (multiplicity) in the oligopeptide transport system which may depend on the structure of the N-terminal amino acid. S-1090 may be dominantly transported via a system that recognizes peptides having histidine as the N-terminal amino acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016287421436
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  • 6
    Electronic Resource
    Electronic Resource
    Transport Characteristics of Ceftibuten (7432-S), a New Oral Cephem, in Rat Intestinal Brush-Border Membrane Vesicles: Proton-Coupled and Stereoselective Transport of Ceftibuten (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 302-307 
    Details
    ISSN: 1573-904X
    Keywords: ceftibuten ; proton-coupled uphill transport ; rat intestinal brush-border membrane vesicles ; stereoselective transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport characteristics of ceftibuten in rat intestinal brush-border membrane vesicles were investigated by a rapid filtration technique. Ceftibuten uptake was markedly stimulated by an inwardly directed H+ gradient (pH 7.5 inside, pH 5.5 outside) in comparison with that in the absence of a H+ gradient. The uptake at 30 sec was four times greater than that observed at equilibrium (overshoot phenomenon), while the H+ gradient-stimulated uptake of ceftibuten was markedly reduced in the presence of FCCP, a protonophore. These results suggested H+-coupled uphill transport of ceftibuten. In contrast, an inwardly directed Na+ gradient had no effect on ceftibuten uptake. The valinomycin-induced K+ diffusion potential (inside positive) significantly stimulated the ceftibuten uptake, suggesting net transfer of the negative charge. In contrast to the cis-isomer ceftibuten, the trans isomer of ceftibuten is not readily absorbed from the intestine, and its uptake was found not to be affected by a H+ gradient. Since the lipophilicity of the trans isomer is similar to that of ceftibuten, the uptake process appears to be stereoselective. The initial uptake of ceftibuten and its analogue cefaclor was concentration dependent under a H+ gradient. The apparent K m value was 0.2 mM for ceftibuten and 3.0 mM for cefaclor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015994323639
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  • 7
    Electronic Resource
    Electronic Resource
    Gelatin-Acacia Microcapsules for Trapping Micro Oil Droplets Containing Lipophilic Drugs and Ready Disintegration in the Gastrointestinal Tract (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1115-1122 
    Details
    ISSN: 1573-904X
    Keywords: nonhardened gelatin–acacia microcapsules ; complex coacervation ; bioavailability ; lipophilic drugs ; O/W emulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nonhardened gelatin-acacia microcapsules were studied for encapsulation of microdroplets of oil solution containing a lipophilic drug as core material and ready disintegration with release of micro oil droplets in the gastrointestinal tract. Probucol and S-312-d, a Ca-channel blocker, were employed as model lipophilic drugs. Glyceryl tricaprylate and tricaprate mixture solutions containing these drugs were encapsulated according to the complex coacervation method and were recovered as free-flowing powders without any hardening (cross-linking) step. The microcapsules obtained were disintegrated, and the emulsion was reproduced within 3 min at 37°C in the first or second test solution defined in the Japanese Pharmacopeia XII. When the microcapsules were stored as a powder at room temperature in a closed bottle, no significant change in their appearance or disintegration time upon rehydration was observed even after 1 year. Oral bioavailabilities of model drugs from the microcapsules were tested in rats and dogs and compared with those from other conventional formulations. Gastrointestinal absorption of both probucol and S-312-d from the microcapsules was remarkably more efficient than that from other formulations such as powders, granules, or oil solution. The proposed method for microencapsulation could be useful for powdering drug-containing oil solutions or O/W emulsions while maintaining excellent bioavailability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018951814939
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  • 8
    Electronic Resource
    Electronic Resource
    Development of Anti-Influenza Virus Drugs I: Improvement of Oral Absorption and In Vivo Anti-Influenza Activity of Stachyflin and Its Derivatives (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1041-1046 
    Details
    ISSN: 1573-904X
    Keywords: influenza ; oral absorption ; PEG ; phosphate ester prodrug ; anti-influenza virus drug
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Stachyflin and its derivatives which are active against the influenza virus in vitro, were studied to improve their reduced in vivo activity after oral administration by chemical modification and some vehicles. Methods. The solubility was examined for different vehicles. The improvement of gastrointestinal absorption was evaluated by the plasma concentration after oral administration to mice or the in situ loop method with rats. The in vivo anti-influenza activity was examined using mice infected with the influenza virus and evaluated based on the virus titer in the lung by TCID50. Results. PEG 400 showed the highest solubility of Stachyflin and its derivative among the vehicles studied. While no viral inhibition was found in the lung after oral administration of 0.5% HPMC suspension of Stachyflin, in vivo anti-influenza virus activity was found with the PEG 400 solution. The absorption of Stachyflin by PEG 400 showed about a fifty-fold increase in AUC compared with that of 0.5% HPMC suspension. Improving the oral absorption of Stachyflin led to an increase in the in vivo anti-influenza virus activity. When the Stachyflin derivative in PEG 4000 was administered orally, there was more enhancement of the oral absorption than with PEG 400. When the aqueous solution of the phosphate ester prodrugs of Stachyflin and its derivative was administered orally, the absorption of the parent compound was improved and in vivo anti-influenza virus activity was found. Conclusions. When Stachyflin and its derivatives were administered orally to mice with a solution in PEG and an aqueous solution of their phosphate ester, their oral absorption was improved and in vivo anti-influenza virus activity was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018983715982
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  • 9
    Electronic Resource
    Electronic Resource
    Epimerization Kinetics of Moxalactam in Frozen Solution (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 266-271 
    Details
    ISSN: 1573-904X
    Keywords: moxalactam ; epimerization ; frozen solution ; ice ; activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The epimerization rate constants of R- and S-epimers of moxalactam (LMOX) in a frozen aqueous solution decreased as the temperature decreased. The reaction proceeded in the unfrozen region remaining in the frozen solution, without being affected by the ice. The reaction stopped completely below the collapse temperature of the LMOX aqueous solution. The ratio of R- and S-epimers at equilibrium, which was equal to the ratio of the epimerization rate constant, increased as the temperature decreased. This change in the ratio at equilibrium could be ascribed to the difference in the activation energy between the two epimers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015918518922
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  • 10
    Electronic Resource
    Electronic Resource
    Lymphatic Transport of Liposome-Encapsulated Drugs Following Intraperitoneal Administration – Effect of Lipid Composition (1985)
    Springer
    Pharmaceutical research 2 (1985), S. 271-278 
    Details
    ISSN: 1573-904X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tumor cells often metastasize through lymphatic channels. It follows that localization of antitumor agents in the lymphatics may be therapeutically beneficial. This study determines the extent to which lipid composition controls lymphatic transport of a model compound (14C-sucrose) in liposomes following intraperitoneal administration in rats. All liposomes tested had mean diameters of approximately 0.2 µm. Liposomes were administerd to thoracic duct cannulated rats, and 14C was quantified in thoracic lymph, several lymph nodes, blood, urine, and peritoneal wash. Changing liposome composition altered the rate of absorption of 14C from the peritoneal cavity, stability in biological fluids, and the relative ability of liposomes to be retained by lymph nodes. Stability in biological fluids (plasma and lymph) appeared to be a reasonable predictor of observed lymph node recovery. Direct measures of lymph node level alone were poor measures of the ability of liposomes to function as prototypal lymphatic drug carriers. Neutral liposomes were better at reaching the general circulation following absorption from the peritoneal cavity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016337500364
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